Semi-Transmissive Liquid Crystal Display Device and Portable Terminal Device

ABSTRACT

A liquid crystal display accommodates a reflective portion with a concavo-convex reflecting pixel electrode for reflecting incident light from the display face side, and a transmissive portion with a transmissive pixel electrode for transmitting light output from the backlight. In a wide viewing angle region, luminance of the reflective portion is greater than the transmissive portion. In other angle regions, luminance of the transmissive portion is greater than the reflective portion. In a wide viewing field mode, the reflective portion and transmissive portion both perform normal display. In the narrow viewing field mode, the transmissive portion performs normal display, while the reflective portion performs cancelling data display, thereby rendering unviewable the display content of the transmissive portion from beyond a certain viewing angle. Thus, a semi-transmissive liquid crystal display device and a portable terminal device is switchable between a narrow viewing field mode and a wide viewing field mode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semi-transmissive liquid crystaldisplay device and a portable terminal having a viewing angle that isswitchable between a narrow viewing field mode and a wide viewing fieldmode.

2. Description of the Related Art

Liquid crystal display devices are widely used in direct-view monitors,projectors, and the like. In the currently used liquid crystal displaydevices, liquid crystals are sealed between two substrates, and theorientation of the liquid crystals is controlled by an electrical fieldapplied to the liquid crystals, whereby information is displayed.

The liquid crystal display devices include transmissive liquid crystaldisplay devices, in which light from a backlight is transmitted througha liquid crystal layer; reflective liquid crystal display devices thatreflect outside light incident on the liquid crystal layer; andsemi-transmissive liquid crystal display devices which have features ofboth the transmissive type and the reflective type, so as to transmitlight from a backlight and to reflect incident light from the outside.

In particular, semi-transmissive liquid crystal display devices, whichhave both the good image quality of the transmissive type and the goodambient light visibility of the reflective type, currently constitutethe mainstream in mobile device applications such as mobile phones andPDAs (Personal Digital Assistance). The semi-transmissive liquid crystaldisplay devices can be further classified as being of internalsemi-transmissive type in which light is reflected in the interior ofthe liquid crystal cells, or of external semi-transmissive type in whichlight is reflected at the exterior of the liquid crystal cells.

As one example of the internal semi-transmissive type, the liquidcrystal display device disclosed in Japanese Laid-Open PatentApplication 11-242226 has been proposed. FIG. 1 is a cross-sectionalview schematically showing the cross sectional arrangement of aprior-art internal semi-transmissive liquid crystal element, and isbased on FIG. 1 appearing in Japanese Laid-Open Patent Application11-242226. As shown in FIG. 1, two substrates 102 are disposed facingeach other over a backlight 109, with a polarizing plate 101 beingprovided to each of the substrates 102 on the side opposite from theseopposing faces. The upper face of the first substrate disposed towardsthe backlight 109 comprises a reflective portion 121 provided with aconcavo-convex reflecting electrode (internal reflecting electrode) 120,and a transmissive portion 122 provided with an electrode 103; the sideof the second substrate that faces the first substrate is provided withan electrode 103 that extends through the reflective portion 121 and thetransmissive portion 122; and a liquid crystal layer 104 is sealedbetween the two substrates 102. Specifically, in an internallyreflective liquid crystal display element of such a design, there areprovided within a single pixel a reflective portion 121 that has aconcavo-convex reflecting electrode (internal reflecting electrode) 120for reflecting incident light from the outside, and a transmissiveportion 122 for transmitting the light of the backlight 109, so thatboth reflected light and transmitted light can be utilized for display.Since the appropriate thickness for the liquid crystals differs betweenthe reflective portion and the transmissive portion, in most cases,liquid crystal thickness is made to differ in the respective portions.In FIG. 1, an insulating film 127 is disposed on the substrate in thereflective portion so that the gap between the concavo-convex reflectingelectrode (internal reflecting electrode) 120 and the facing electrode103 in the reflective portion 121 is smaller than the gap between theelectrodes 103 in the transmissive portion 122, and the concavo-convexreflecting electrode (internal reflecting electrode) 120 is formed overthe insulating film 127.

One example of the external semi-transmissive type is the liquid crystaldisplay device disclosed in Japanese Laid-Open Patent Application2000-180819. FIG. 2 is a cross-sectional view schematically showing thecross sectional arrangement of a prior-art external semi-transmissiveliquid crystal element, and is based on FIG. 1 appearing in JapaneseLaid-Open Patent Application 2000-180819. As shown in FIG. 2, the liquidcrystal display device is provided with a backlight 109; over thebacklight 109 two substrates 102 are arranged facing each other,electrodes 103 are provided on the opposing faces of the pair ofsubstrates 102, and a liquid crystal layer 104 is sandwiched between theelectrodes 103. A reflective polarizing plate 123 is disposed on thesubstrate 102 on the side that faces the backlight 109; and a polarizingplate 101 is provided so as to cover the surface of the reflectivepolarizing plate 123. A polarizing plate 101 is also provided to thesubstrate 102 that faces the first substrate. The plate is formed on thesubstrate side that is on the opposite side from the backlight 109. Inthis prior art example, transmissive display is carried out with thelight of the backlight 109. During reflective display, however, specificpolarized light of the light incident from the display face is reflectedby the reflective polarizing plate 123, and the reflected light exitstowards the observer, forming the displayed image. In this case, thetransmissive portion and the reflective portion are in the samelocation, and a single pixel functions as a transmitting/reflectiveportion 124. A characteristic of systems in which reflective polarizingplates are used in the prior art is that the voltage-transmissivitycurve (reflectivity) is reversed between transmissive display andreflective display.

In regard to the display element using a reflective polarizing platedisclosed in Japanese Laid-Open Patent Application 2000-193962, adescription is given of a display element in which the samevoltage-transmissivity (reflectivity) curves are obtained for atransmissive display and a reflective display through the use of a phasedifference plate.

The liquid crystal display device disclosed in Japanese Laid-Open PatentApplication 2003-098325 employs a different method based on an externalreflective system. FIG. 3 is a cross-sectional view schematicallyshowing the cross sectional arrangement of a prior-art externalsemi-transmissive liquid crystal element, and is based on FIG. 15appearing in Japanese Laid-Open Patent Application 2003-098325. As shownin FIG. 3, above a backlight 109, two substrates 102 are arranged facingeach other, electrodes 103 are provided to the substrates on theopposing faces thereof, and a liquid crystal layer 104 is sealed betweenthe electrodes 103. Polarizing plates 101 are provided to each of thesubstrates 102 on the side opposite from their opposing faces. Thepolarizing plate 101 that faces the backlight 109 is provided with asemi-transmissive reflecting plate 125, which is disposed on the side ofthe plate that faces the backlight. The liquid crystal display elementconstitutes a transmitting/reflective portion 126. Specifically, in thisprior-art liquid crystal display element, a semi-transmissive reflectingplate 125, rather than a polarized light reflecting plate, is disposedbetween the backlight 109 and the polarizing plate 101 disposed towardsthe backlight 109. In this case, in contrast to Japanese Laid-OpenPatent Application 2000-180819, the same voltage-transmissivity(reflectivity) curves are obtained for a transmissive display and areflective display.

In recent years, there has been a need for display devices to have aprivacy protecting function whereby people other than the person viewingthe device, namely, people close by, cannot view the device. Forexample, in the case of a banking terminal known as ATM (AutomatedTeller Machine) or the like, it is necessary to touch number buttons ona display device in order to input a Personal Identification Number, andsuch a display device must be prevented from being observed by others.Similarly, in the case of a mobile phone as well, there is a need for afunction to prevent persons disposed close to the user from being ableto see displayed information. Furthermore, in the case of PDAs andnotebook personal computers (hereinafter also referred to as notebookPCs) as well, there is a similar need for a function to prevent nearbypersons from being able to view the screen in trains or other forms ofpublic transportation.

On the other hand, there are instances in which there is a need for adisplay device to be viewed by several individuals. For example, whentelevision images are displayed on the screen of a mobile phone or thelike, there are instances in which it would be desirable to show themobile phone to a nearby individual in addition to the owner. There arealso instances in which a data screen of a notebook PC is viewed byseveral people.

Consequently, a display device may have a narrow viewing field mode foruse in individual viewing of highly confidential information, and a wideviewing field mode for use in viewing highly public information byseveral people. Moreover, in the case of mobile phones, PDAs, andnotebook PCs, there is a need for a display device switchable betweenthese display modes.

The liquid crystal display device disclosed in Japanese Laid-Open PatentApplication 10-153968 is a display device capable of being switchedbetween a narrow viewing field mode and a wide viewing field mode. FIG.4 is a plan view showing the pixel arrangement of the liquid crystaldisplay device disclosed in Japanese Laid-Open Patent Application10-153968. FIG. 5 is the voltage-transmissivity plot for a wide viewingfield area during viewing in a narrow field as described in the patentdocument, and FIG. 6 is the voltage-transmissivity plot for a wideviewing field area during viewing in a wide field as described in thepatent document.

As shown in FIG. 4, the active matrix liquid crystal display devicedisclosed in Japanese Laid-Open Patent Application 10-153968 comprises aplurality of pixels 111 in which liquid crystals are sealed betweentransparent electrodes and are arranged in matrix form. Each pixel 111comprises a first pixel region 112 connected to a control line 116, anda second pixel region 113 connected to the first pixel region via acapacitor 114; and a switching element 115 is provided between the firstpixel region 112 and the second pixel region 113.

Here, operation when the liquid crystal mode is the TN (Twisted Nematic)mode shall be described. During viewing in a narrow field, the switchingelement 115 is shorted. Since the first pixel region 112 and the secondpixel region 113 are directly connected, the same voltage (V1) as thatof the control line 116 is fed to the first pixel region 112 and thesecond pixel region 113. Since the first pixel electrode in the firstpixel region 112 and the second pixel electrode in the second pixelregion 113 are at identical voltage, operation is the same as in normalTN mode. As shown in FIG. 5, the grayscale inversion characteristic ofthe TN mode appears in the voltage-transmissivity curve in the wideviewing range of the pixel 111 as a whole. This characteristic combinesthe voltage-transmissivity curves of the first pixel region 112 and thesecond pixel region 113.

On other hand, during viewing in a wide field, the switching element 115is open. Since the first pixel region 112 and the second pixel region113 are connected via the capacitor 114, the driving voltage applied tothe control line 116 (voltage V1) is supplied unchanged to the firstpixel region 112 while being supplied to the second pixel region 113 viathe capacitor 114 (voltage V2). Thus, the voltage supplied to the firstpixel region 112 is different from the voltage supplied to the secondpixel region 113. Specifically, the second pixel voltage in the secondpixel region 113 connected via the capacitor 114 has an absolute valuethat is less than the value of the first pixel voltage in the firstpixel region 112 (|V1|>|V2|). As shown in FIG. 6, by means of applyingdifferent voltages to the first pixel region 112 and the second pixelregion 113, the voltage-transmissivity curve 118 in the wide viewingrange of first pixel region 112 has a waveform different from that ofthe voltage-transmissivity curve 119 in the wide viewing range of secondpixel region 113; and the voltage-transmissivity curve 117 b in the wideviewing range of the pixel 111 as a whole, which curve combines thevoltage-transmissivity curve of the first pixel region 112 and thevoltage-transmissivity curve of the second pixel region 113, assumes asmooth curve free from grayscale inversion.

That is, in the prior art disclosed in Japanese Laid-Open PatentApplication 10-153968, the viewing angle is switched between a wideviewing field mode and a narrow viewing field mode by changing thevoltage-transmissivity characteristics of the pixels and varying theviewing angle characteristics of the liquid crystal panel. Table 1summarizes differences in the voltages applied to the first pixel regionand the second pixel region in the wide viewing field mode in relationto the narrow viewing field mode. In the wide viewing field mode, thevoltages applied to the first pixel region and the second pixel regionare different, while in the narrow viewing field mode the voltages arethe same.

TABLE 1 Wide viewing field mode Narrow viewing field mode First pixelSecond pixel First pixel Second pixel region region region regionApplied Applied Applied Applied voltage V1 voltage V2 voltage V1 voltageV1

In Japanese Laid-Open Patent Application 09-006289, there is described aliquid crystal display device wherein single pixels are composed of aplurality of sub-pixels having different orientation characteristics,with the sub-pixels being connected to control lines for independentlycontrolling the operation thereof. The operator operates a switchwhereby sub-pixels for applying control signals via a control line groupare selected from the pixels, and the viewing angle of the displayelement is switched between a wide viewing angle designed to facilitateviewing by the operator, and a narrow viewing angle designed to preventobservation by a third party.

However, the display devices that enable switching between a narrowviewing field mode and a wide viewing field mode have problems such asthe following. First, in the liquid crystal display device disclosed inJapanese Laid-Open Patent Application 10-153968, in the narrow viewingfield mode of a transmissive display, grayscale inversion is producedfor an observer whose views the display at a wide viewing angle.However, depending on the type of display, the observer would still beable to view the display at a wide viewing angle despite the presence ofgrayscale inversion. Furthermore, switching of the viewing angle in areflective display is not disclosed in relation to this system, and nomeasures are envisioned that would allow the viewing angle of thesemi-transmissive liquid crystal display device to be switched. In theliquid crystal display device disclosed in Japanese Laid-Open PatentApplication 09-006289 as well, there is no mention of switching theviewing angles of a reflective display, and no measures are envisionedthat would allow the viewing angle of the semi-transmissive liquidcrystal display device to be switched.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a semi-transmissiveliquid crystal display device and a portable terminal device that enableswitching of the viewing angle between a narrow viewing field mode and awide viewing field mode.

The semi-transmissive liquid crystal display device according to thepresent invention comprises a liquid crystal panel provided with aliquid crystal layer between two substrates having electrodes formedthereon; a backlight for outputting light to this liquid crystal panel;and a controller for controlling a voltage applied to the liquid crystallayer; wherein each pixel of the liquid crystal panel individually has areflective portion for reflecting light incident from the display screenside, and a transmissive portion for transmitting and displaying lightthat is output by the backlight; both the reflective portion and thetransmissive portion have wide viewing angle characteristics, and haveluminance/viewing angle characteristics such that in a wide viewingangle region greater than a certain angle the luminance of thereflective portion is greater than the luminance of the transmissiveportion, whereas in other angle regions the luminance of thetransmissive portion is greater than the luminance of the reflectiveportion; and the controller controls, independently for the reflectiveportion and the transmissive portion, the voltage applied to the liquidcrystal layer, and switches a viewing angle between a wide viewing fieldmode and a narrow viewing field mode by performing control so that inthe wide viewing field mode the reflective portion performs normaldisplay or dark display while the transmissive portion performs normaldisplay, whereas in the narrow viewing field mode the reflective portionperforms cancelling data display (pseudo-information display to cancelor disappear normal display by the transmissive portion) while thetransmissive portion performs normal display.

In the narrow viewing field mode, an image pattern can be displayed byperforming normal display or dark display in the reflective portion thatmakes up part of the pixel, without carrying out cancelling datadisplay. In the narrow viewing field mode, by displaying an imagepattern viewable from the wide viewing angle, styling can be improved ascompared to the case where nothing is visible.

The semi-transmissive liquid crystal display device according to thepresent invention comprises a liquid crystal panel provided with aliquid crystal layer between two substrates having electrodes formedthereon; a backlight for outputting light to this liquid crystal panel;and a controller for controlling a voltage applied to the liquid crystallayer; wherein each pixel of the liquid crystal panel individually has areflective portion for reflecting light incident from the display screenside, and a transmissive portion for transmitting and displaying lightthat is output by the backlight; each of the reflective portion and thetransmissive portion has wide viewing angle characteristics and narrowviewing angle characteristics; and the controller controls,independently for the reflective portion and the transmissive portion,the voltage applied to the liquid crystal layer, and switches a viewingangle between a wide viewing field mode and a narrow viewing field modeby performing control so that in the wide viewing field mode thereflective portion performs normal display while the transmissiveportion performs normal display, whereas in the narrow viewing fieldmode the reflective portion performs dark display while the transmissiveportion performs normal display.

In the narrow viewing field mode, an image pattern can be displayed byperforming normal display in the reflective portion that makes up partof the pixel, without carrying out dark display. In the narrow viewingfield mode, by displaying an image pattern viewable from the wideviewing angle, styling can be improved as compared to the case wherenothing is visible.

The semi-transmissive liquid crystal display device according to thepresent invention comprises a liquid crystal panel provided with aliquid crystal layer between two substrates having electrodes formedthereon; a backlight for outputting light to this liquid crystal panel;and a controller for controlling a voltage applied to the liquid crystallayer; wherein each pixel of the liquid crystal panel individually has areflective portion for reflecting light incident from the display screenside, and a transmissive portion for transmitting and displaying lightthat is output by the backlight; each of the reflective portion and thetransmissive portion has wide viewing angle characteristics and narrowviewing angle characteristics; and the controller controls,independently for the reflective portion and the transmissive portion,the voltage applied to the liquid crystal layer, and switches a viewingangle between a wide viewing field mode and a narrow viewing field modeby performing control so that in the wide viewing field mode thereflective portion performs normal display while the transmissiveportion performs normal display, whereas in the narrow viewing fieldmode the reflective portion performs normal display while thetransmissive portion performs dark display.

In the narrow viewing field mode, an image pattern can be displayed byperforming normal display in the transmissive portion that makes up partof the pixel, without carrying out dark display. In the narrow viewingfield mode, by displaying an image pattern viewable from the wideviewing angle, styling can be improved as compared to the case wherenothing is visible.

In preferred practice, the display of the image pattern in the narrowviewing field mode will vary spatially, temporally, or spatiotemporally.By so doing, it is possible to prevent the original display content frombecoming viewable due to eye adaptation.

The voltage applied to the liquid crystal layer in the reflectiveportion and in the transmissive portion can be independently controlledby separately providing a reflection pixel electrode formed in thereflective portion, and a transmission pixel electrode formed in thetransmissive portion, and connecting the electrodes to mutuallydifferent TFTs (Thin Film Transistors).

The voltage applied to the liquid crystal layer in the reflectiveportion and in the transmissive portion can be independently controlledby separately providing a COM electrode formed in the reflective portionand a COM electrode formed in the transmissive portion.

The semi-transmissive liquid crystal display device according to thepresent invention comprises a liquid crystal panel provided with aliquid crystal layer between two substrates having electrodes formedthereon; a backlight for outputting light to this liquid crystal panel;a reflective polarizing plate or a semi-transmissive polarizing plate onthe substrate disposed toward the backlight, on the side of thesubstrate that faces the backlight; and a controller for controlling avoltage applied to the liquid crystal layer; wherein each pixel of theliquid crystal panel individually has a first display portion and asecond display portion; both the first display portion and the seconddisplay portion have wide viewing angle characteristics, and haveluminance/viewing angle characteristics such that in a wide viewingangle region greater than a certain angle the luminance of the firstdisplay portion is greater than the luminance of the second displayportion, whereas in other angle regions the luminance of the seconddisplay portion is greater than the luminance of the first displayportion; and the controller controls, independently for the firstdisplay portion and the second display portion, the voltage applied tothe liquid crystal layer, and switches a viewing angle between a wideviewing field mode and a narrow viewing field mode by performing controlso that in the wide viewing field mode the first display portionperforms normal display or dark display while the second display portionperforms normal display, whereas in the narrow viewing field mode thefirst display portion performs cancelling data display while the seconddisplay portion performs normal display.

In the narrow viewing field mode, an image pattern can be displayed byperforming normal display or dark display in the first display portionthat makes up part of the pixel, without carrying out cancelling datadisplay. In the narrow viewing field mode, by displaying an imagepattern viewable from the wide viewing angle, styling can be improved ascompared to the case where nothing is visible. Furthermore, in preferredpractice, the display of the image pattern in the narrow viewing fieldmode will vary spatially, temporally, or spatiotemporally. By so doing,it is possible to prevent the original display content from becomingviewable due to eye adaptation.

The voltage applied to the liquid crystal layer in the first displayportion and in the second display portion can be independentlycontrolled by independently providing a first pixel electrode formed inthe first display portion, and a second pixel electrode formed in thesecond display portion, and connecting the electrodes to mutuallydifferent TFTs. The voltage applied to the liquid crystal layer in thefirst display portion and in the second display portion can beindependently controlled by separately providing a COM electrode formedin the first display portion and a COM electrode formed in the seconddisplay portion.

As the cancelling data, white luminance, intermediate luminance, orpseudo-colored light may be used. It suffices for the cancelling data tobe any display that allows the original displayed content to be viewedbeyond a specific viewing angle. By means of displaying cancelling datain the narrow viewing field mode, the original displayed content can notbe viewed from a wide viewing angle due to reflected light.

A front light may be provided on the side facing the observer. By sodoing, even where outside light is absent or weak, sufficient luminancewill be provided by the front light, and switching of the viewing anglewill function.

A louver may be provided for use in regulating the direction of exitinglight incident from the backlight. By so doing, it is possible toimprove the viewing angle characteristics of the narrow viewing field inthe transmissive portion.

A transmitting/scattering switch element switchable between a state oftransmitting incident light and a state of scattering incident light maybe provided for use. By so doing, it becomes possible for thetransmissive portion to switch the viewing angle by means of thetransmitting/scattering switch element, and the viewing angle can beefficiently switched by the combined use of display switching in thereflective portion.

In the present invention, using the aforementioned semi-transmissiveliquid crystal display device in a portable terminal device allows theuser to set optimal display conditions according to the serviceenvironment of the portable terminal device.

According to the present invention, there can be provided asemi-transmissive liquid crystal display device wherein each pixel ofthe liquid crystal display element is separately provided with areflective portion and a transmissive portion, making it possible toswitch the viewing angle between a wide viewing field mode and a narrowviewing field mode by independently controlling the voltages applied tothe liquid crystal layer in the reflective portion and the transmissiveportion. Even with an external semi-transmissive liquid crystal displaydevice in which a liquid crystal display element serves as both areflective portion and a transmissive portion, it is possible to providea semi-transmissive liquid crystal display device wherein each pixel isseparately provided with first display portion in which reflectivedisplay is primarily used, and a second display portion in whichtransmissive display is primarily used, making it possible to switch theviewing angle between a wide viewing field mode and a narrow viewingfield mode by independently controlling the voltages applied to theliquid crystal layer in the first display portion and second displayportion. By means of the present invention, the viewing angle of asemi-transmissive liquid crystal display device having a reflectivedisplay portion can be switched in a manner not supported in the priorart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing the crosssectional arrangement of a prior-art internal semi-transmissive liquidcrystal element, and is based on FIG. 1 appearing in Japanese Laid-OpenPatent Application 11-242226;

FIG. 2 is a cross-sectional view schematically showing the crosssectional arrangement of a prior-art external semi-transmissive liquidcrystal element, and is based on FIG. 1 appearing in Japanese Laid-OpenPatent Application 2000-180819;

FIG. 3 is a cross-sectional view schematically showing the crosssectional arrangement of a prior-art external semi-transmissive liquidcrystal element, and is based on FIG. 15 appearing in Japanese Laid-OpenPatent Application 2003-098325;

FIG. 4 is a plan view showing the pixel arrangement of the liquidcrystal display device disclosed in Japanese Laid-Open PatentApplication 10-153968;

FIG. 5 is the voltage-transmissivity plot for a wide viewing field areaduring viewing in a narrow field as described in Japanese Laid-OpenPatent Application 10-153968;

FIG. 6 is the voltage-transmissivity plot for a wide viewing field areaduring viewing in a wide field as described in Japanese Laid-Open PatentApplication 10-153968;

FIG. 7 is a cross-sectional view of an internal semi-transmissive liquidcrystal display device according to a first embodiment of the presentinvention;

FIG. 8 is a schematic diagram of the electrodes on the TFT substrate andthe electrode on the opposing substrate in the first embodiment, whereinFIG. 8A is a schematic plan view of the electrodes on the TFT substrate,and FIG. 8B is a schematic plan view of the electrode on the opposingsubstrate;

FIG. 9 is a curve showing the viewing angle-luminance characteristicsduring viewing in a narrow field in the first embodiment of the presentinvention;

FIG. 10 is a cross-sectional view of an internal semi-transmissiveliquid crystal display device according to a second embodiment of thepresent invention;

FIG. 11 is a schematic diagram of the electrode on the TFT substrate andthe electrodes on the opposing substrate in the second embodiment,wherein FIG. 11A is a schematic plan view of the electrode on the TFTsubstrate, and FIG. 11B is a schematic plan view of the electrodes onthe opposing substrate;

FIG. 12 is a cross-sectional view of an internal semi-transmissiveliquid crystal display device according to a third embodiment of thepresent invention;

FIG. 13 is a schematic diagram of the electrodes on the TFT substrate inthe third embodiment;

FIG. 14 is a cross-sectional view of an internal semi-transmissiveliquid crystal display device according to a fourth embodiment of thepresent invention;

FIG. 15 is a schematic diagram of the electrodes on the TFT substrate inthe fourth embodiment;

FIG. 16 is a cross-sectional view of an internal semi-transmissiveliquid crystal display device according to a fifth embodiment of thepresent invention, wherein FIG. 16A shows operation during viewing in awide field, and FIG. 16B shows operation during viewing in a narrowfield;

FIG. 17 is a cross-sectional view of an internal semi-transmissiveliquid crystal display device according to a sixth embodiment of thepresent invention, wherein FIG. 17A shows operation during viewing in awide field, and FIG. 17B shows operation during viewing in a narrowfield;

FIG. 18 is a cross-sectional view of an internal semi-transmissiveliquid crystal display device according to a seventh embodiment of thepresent invention;

FIG. 19 is a cross-sectional view of an internal semi-transmissiveliquid crystal display device according to an eighth embodiment of thepresent invention;

FIG. 20 is a cross-sectional view of an external semi-transmissiveliquid crystal display device provided with a polarized light reflectingplate according to a ninth embodiment of the present invention;

FIG. 21 is a cross-sectional view of an external semi-transmissiveliquid crystal display device provided with a semi-transmissivereflecting plate according to a modified example of the ninth embodimentof the present invention;

FIG. 22 is a diagram showing the operation in the viewing anglecontroller and the pixel units of the display portion in a wide viewingfield mode (FIG. 22A) and a narrow viewing field mode (FIG. 22B) of thefirst to fourth and ninth embodiments of the present invention;

FIG. 23 is a diagram showing the operation in the viewing anglecontroller and the pixel units of the display portion in a narrowviewing field mode in a tenth embodiment of the present invention;wherein FIG. 23A shows operation of some of the viewing anglecontrollers performing normal display, and FIG. 23B shows operation ofvarying the image pattern;

FIG. 24 is a diagram showing the operation in the viewing anglecontroller and the pixel units of the display portion in a wide viewingfield mode (FIG. 24A) and a narrow viewing field mode (FIG. 24B) of thefifth and sixth embodiments of the present invention;

FIG. 25 is a diagram showing the operation in the viewing anglecontroller and the pixel units of the display portion in a narrowviewing field mode in an eleventh embodiment of the present invention;wherein FIG. 25A shows operation of some of the viewing anglecontrollers performing normal display, and FIG. 25B shows operation ofvarying the image pattern; and

FIG. 26 is a perspective view showing a portable terminal deviceequipped with the liquid crystal display device according to a twelfthembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The semi-transmissive liquid crystal display device and portableterminal device according to the embodiments of the present inventionshall be described in detail hereinbelow with reference to the drawings.First, a semi-transmissive liquid crystal display device according to afirst embodiment of the invention shall be described. FIG. 7 is across-sectional view of an internal semi-transmissive liquid crystaldisplay device according to the first embodiment; and FIG. 8 is aschematic diagram of the electrodes on the TFT substrate and theelectrode on the opposing substrate in the first embodiment. Table 2 isa first illustration that shows operation of the reflective portion andthe transmissive portion in a wide viewing field mode and a narrowviewing field mode in the first embodiment; and Table 3 is a secondillustration that shows operation of the reflective portion and thetransmissive portion in a wide viewing field mode and a narrow viewingfield mode in the first embodiment. FIG. 9 is a curve showing theviewing angle-luminance characteristics during viewing in a narrow fieldin the first embodiment.

First, the design of a single pixel of the semi-transmissive liquidcrystal display device according to the first embodiment shall bedescribed using FIGS. 7 and 8. As shown in FIG. 7, two substrates 12 arearranged facing each other on top of a backlight 6, and a COM electrode13 is disposed on the substrate 12 disposed towards the observer (theupper side in the drawing), which is the direction that light exits thebacklight (this substrate shall be termed the opposing substrate), andon the side of the substrate that faces the backlight 6. The substrate12 that is disposed towards the backlight 6 is provided, on the sidefacing the opposing substrate, with a concavo-convex reflecting pixelelectrode (internal reflecting plate) 14 whose surface has aconcavo-convex shape and which reflects light incident from the observerside, and a transmissive pixel electrode 15 for transmitting light thatis output by the backlight 6 (this substrate shall be termed the TFTsubstrate). The liquid crystal panel of the liquid crystal displaydevice in the present embodiment thus comprises a reflective portion 17provided with the concavo-convex reflecting pixel electrode (internalreflecting plate) 14, and a transmissive portion 18 provided with thetransmissive pixel electrode 15. A liquid crystal layer 16 is sandwichedbetween the two substrates, but since the reflective portion 17 and thetransmissive portion 18 have different optimal liquid crystalthicknesses, a step is provided along the TFT substrate so that the gapbetween the concavo-convex reflecting pixel electrode 14 and the COMelectrode 13 in contraposition thereto is smaller than the gap betweenthe transmissive pixel electrode 15 and the COM electrode 13 incontraposition thereto, whereby the liquid crystal of the reflectiveportion 17 is made thinner. In FIG. 7, the step has been produced on theTFT substrate, but the step could be disposed on the opposing substrateinstead. The opposing substrate and the TFT substrate are bondedtogether with the liquid crystal layer 16 sandwiched therebetween, andpolarizing plates 11 are disposed on the opposing substrate and on theTFT substrate, on the sides of the substrates that are opposite from theopposing faces thereof.

FIG. 8A is a schematic plan view of the electrodes on the TFT substrate,and shows the structure of the electrodes on the TFT substrate shown inFIG. 7 as viewed from the upper face of the substrate. As shown in FIG.8A, the concavo-convex reflecting pixel electrode (internal reflectingplate) 14 and the transmissive pixel electrode 15 are disposed insections defined by grid-form data lines 19 and gate lines 20,respectively. A concavo-convex reflecting pixel electrode TFT 21 isformed in proximity to the intersection point of the data line 19 andthe gate line 20 in the section in which the concavo-convex reflectingpixel electrode (internal reflecting plate) 14 is disposed, and theconcavo-convex reflecting pixel electrode (internal reflecting plate) 14is connected to the source electrode of the concavo-convex reflectingpixel electrode TFT 21. Similarly, a transmissive pixel electrode TFT 22is formed in proximity to the intersection point of the data line 19 andthe gate line 20 in the section that accommodates the transmissive pixelelectrode 15, and the transmissive pixel electrode 15 is connected tothe source electrode of the transmissive pixel electrode TFT 22. Thatis, in order to make it possible to apply different voltages to thereflective portion 17 provided with the concavo-convex reflecting pixelelectrode (internal reflecting plate) 14 and to the transmissive portion18 provided with the transmissive pixel electrode 15, different TFTs areconnected to the concavo-convex reflecting pixel electrode 14 and thetransmissive pixel electrode 15. FIG. 88 is a schematic plan view of theelectrode on the opposing substrate. As shown in FIG. 88, the COMelectrode 13 on the opposing substrate is shared by the reflectiveportion 17 and the transmissive portion 18.

Next, the operation of the first embodiment shall be described usingFIG. 7, Table 2, and FIG. 9. Where display is performed with thesemi-transmissive liquid crystal display device of the presentembodiment, light incident on the display face from the observer side inthe reflective portion 17 is passed through the liquid crystal layer 16,is subsequently reflected by the concavo-convex reflecting pixelelectrode (internal reflecting plate) 14, is then again passed throughthe liquid crystal layer 16, and is output as display light from thedisplay face. Meanwhile, in the transmissive portion 18, light that isoutput from the backlight 6 passes through the transmissive pixelelectrode 15, and after passing through the liquid crystal layer 16 isoutput as display light from the display face. At this time, thevoltages across the electrodes in the reflective portion 17 and thetransmissive portion 18 are controlled independently, whereby theorientation of the liquid crystals in the reflective portion 17 and thetransmissive portion 18 can be controlled, making it possible to controlthe display conditions. The transmissive portion has the viewing anglecharacteristics of the wide viewing field that allow wide-viewing fielddisplay to be maintained in an independent manner.

TABLE 2 Wide viewing field mode Narrow viewing field mode ReflectiveTransmissive Reflective Transmissive portion portion portion portionNormal Normal Bright Normal display display display

As shown in FIG. 2, in a wide viewing field mode, the transmissiveportion performs normal display, and the reflective portion performsnormal display as well. In a narrow viewing field mode, on the otherhand, the transmissive portion performs normal display, but thereflective portion assumes the bright condition (white display). Asshown in FIG. 9, by designing the luminance 2 of the reflective portionso as to be greater than the luminance 1 of the transmissive portionwith respect to viewing angles greater than a specific angle (i.e., therange 3 of restricted viewing angles), the display content of thetransmissive portion becomes unviewable from within the range 3 ofrestricted viewing angles. That is, the reflective portion can berepresented as a viewing angle controller, and the transmissive portionas the display portion. Consequently, switching between the wide viewingfield mode and the narrow viewing field mode is possible by switchingthe display of the reflective portion (viewing angle controller). InFIG. 9, a viewing angle of 0° represents the direction perpendicular tothe liquid crystal panel.

In a narrow viewing field mode the reflective portion is not limited tothe bright condition (white display) of the three pixels R (red), G(green), and blue (B), and an intermediate luminance or a pseudo-colordisplay is acceptable instead as long as the display content of thetransmissive portion is unviewable from within the range 3 of restrictedviewing angles.

In the first embodiment, in a wide viewing field mode, the reflectiveportion may perform normal display while the reflective portion performsdark display (black display), as shown in Table 3. In the case of Table2, normal display is performed in the reflective portion in a wideviewing field mode, whereby it is possible for display content to beviewed by means of outside light, whereas in the case of Table 3, thereflective portion does not perform normal display in a wide viewingfield mode, making it difficult for display content to be viewed bymeans of outside light.

TABLE 3 Wide viewing field mode Narrow viewing field mode ReflectiveTransmissive Reflective Transmissive portion portion portion portionDark Normal Bright Normal display display

The liquid crystal mode for operating in a vertical electric field ispreferably a wide-viewing angle VA (Vertical Alignment) mode. Examplesof VA modes are multi-domain ones affording reduced viewing angledependence, such as the MVA (Multi-domain Vertical Alignment) format,the EVA (Patterned Vertical Alignment) format, and the ASV (AdvancedSuper V) format. Furthermore, the present invention is suitable for usein liquid crystal display panels of a film-compensated TN mode.

According to the present embodiment, there can be provided asemi-transmissive liquid crystal display device wherein each pixel ofthe liquid crystal display element is separately provided with areflective portion and a transmissive portion, making it possible toswitch the viewing angle between a wide viewing field mode and a narrowviewing field mode by independently controlling the voltages applied tothe liquid crystal layer in the reflective portion and the transmissiveportion. By means of the present embodiment, the viewing angle of asemi-transmissive liquid crystal display device having a reflectivedisplay portion can be switched in a manner not supported in the priorart.

Next, a second embodiment of the present invention shall be described.In the first embodiment, the pixel electrodes of the reflective portionand the display portion on the TFT substrate are connected to differentTFTs, making possible independent control of the voltages of thereflective portion and the display portion. In the second embodiment ofthe present invention, a pixel electrode is shared by the reflectiveportion and the display portion on the TFT substrate and is controlledby a single TFT, while the COM electrode of the reflective portion andthe COM electrode of the display portion of the display portion areseparate. FIG. 10 is a cross-sectional view of an internalsemi-transmissive liquid crystal display device according to the secondembodiment. FIG. 11 is a schematic diagram of the electrode on the TFTsubstrate and the electrodes on the opposing substrate in the secondembodiment.

The arrangement of the second embodiment shall be described using FIGS.10 and 11. The elements in FIG. 10 that are identical to those in FIG. 7have been assigned identical symbols, while the elements in FIG. 11 thatare identical to those in FIG. 8 have been assigned identical symbolsand shall not be discussed in detail. As shown in FIG. 10, theconcavo-convex reflecting pixel electrode (internal reflecting plate) 14disposed on the substrate 12 is shorted with the transmissive pixelelectrode 15 to form a single pixel electrode 25. Consequently, as shownin FIG. 11A, a single pixel electrode TFT 26 will suffice as the TFT forconnection to the pixel electrode 25. On the other hand, as shown inFIGS. 10 and 11, the opposing substrate is provided with the COMelectrodes as a separate COM electrode 23 of a reflective portion and aseparate COM electrode 24 of a transmissive portion. These electrodesare provided respectively to the reflective portion 17 and thetransmissive portion 18, making it possible for different voltages to beapplied to these portions in a respective fashion.

Since the COM electrode 23 of the reflective portion and the COMelectrode 24 of the transmissive portion are made separate in this way,it is possible to independently control the voltages of the reflectiveportion and the transmissive portion, thereby affording operation andworking effects analogous to those of the first embodiment.

Next, a third embodiment of the present invention shall be described.Whereas the first embodiment employs a mode in which the liquid crystalsare operated in a vertical electric field, the third embodiment of thepresent invention differs therefrom in that the liquid crystals areoperated in a lateral electric field. FIG. 12 is a cross-sectional viewof an internal semi-transmissive liquid crystal display device accordingto the third embodiment. FIG. 13 is a schematic diagram of theelectrodes on the TFT substrate in the third embodiment.

The arrangement of the third embodiment shall be described using FIGS.12 and 13. In FIG. 12, elements identical to those in FIG. 7 have beenassigned identical symbols and shall not be discussed in detail. Asshown in FIG. 12, the liquid crystal panel is disposed above a backlight6, and the substrate 12 disposed towards the backlight 6 comprises areflective portion 17 in which an internal reflecting plate 41 isformed, and also comprises a transmissive portion 18 for transmittinglight that is output from the backlight. In the IPS (In Plane Switching)mode of operation in a lateral electric field in a direction horizontalin relation to the substrate, it is preferable for the liquid crystalinterface to be planar, and for this reason a planarizing film 42 isformed over the internal reflecting plate 41. A reflective pixelelectrode 40 and a COM electrode 13 are formed in a comb-toothconfiguration on the planarizing film 42; and a transmissive pixelelectrode 15 and a COM electrode 13 are formed in a comb-toothconfiguration on the substrate 12 in the transmissive portion 18. Thestructure of these electrodes is shown in plan view from the upper faceof the substrate in FIG. 13. As shown in FIG. 13, the reflective portion17 and the transmissive portion 18 are partitioned by data lines 19 andgate lines 20 disposed in a grid arrangement, with the electrodes beingformed in a comb-tooth configuration in the regions. In the presentembodiment, while the COM electrodes of the reflective portion 17 andthe transmissive portion 18 are at the same potential, the reflectivepixel electrode 40 and the transmissive pixel electrode 15 are connectedto a reflective pixel electrode TFT 21 and a transmissive pixelelectrode TFT 22, respectively, so that the voltages of the reflectiveportion 17 and the transmissive portion 18 are controllableindependently. Since it is possible to independently control thevoltages of the reflective portion and the transmissive portion, theoperation and working effects are analogous to those of the firstembodiment.

While the arrangement and placement of electrodes would differ somewhat,this design could be used favorably in similar embodiments such as theFFS (Fringe Field Switching) format or AFFS (Advanced Fringe FieldSwitching) format.

Next, a fourth embodiment of the present invention shall be described.Whereas in the third embodiment, the pixel electrodes of the reflectiveportion and the display portion have respective TFTs connected thereto,in the fourth embodiment of the present invention, the reflectiveportion and the display portion share a pixel electrode, while the COMelectrode of the reflective portion and the COM electrode of the displayportion are separate. FIG. 14 is a cross-sectional view of an internalsemi-transmissive liquid crystal display device according to the fourthembodiment. FIG. 15 is a schematic diagram of the electrodes on the TFTsubstrate in the fourth embodiment.

The arrangement of the fourth embodiment shall be described using FIGS.14 and 15. In FIG. 14, elements identical to those in FIG. 12 have beenassigned identical symbols and shall not be discussed in detail. Asshown in FIG. 14, in the IPS (In Plane Switching) mode of operation in alateral electric field in a direction horizontal in relation to thesubstrate, it is preferable for the liquid crystal interface to beplanar, and for this reason a planarizing film 42 is formed over theinternal reflecting plate 41. A pixel electrode 25 and a COM electrode23 of the reflective portion are formed in a comb-tooth configuration onthe planarizing film 42; and a pixel electrode 25 and a COM electrode 24of the transmissive portion are formed in a comb-tooth configuration onthe substrate 12 in the transmissive portion 18. The structure of theseelectrodes is shown in plan view from the upper face of the substrate inFIG. 15. As shown in FIG. 15, the pixel electrodes 25 are connected to asingle pixel electrode TFT 26. The COM electrodes, meanwhile, aredivided into the COM electrode 23 of the reflective portion 17 and theCOM electrode 24 of the transmissive portion 18, making it possible fordifferent voltages to be applied. Since it is possible to independentlycontrol the voltages of the reflective portion and the transmissiveportion, the operation and working effects are analogous to those of thefirst embodiment.

Next, a fifth embodiment of the present invention shall be described. Inthe first through fourth embodiments, cancelling data is displayed onthe viewing angle controller in a narrow viewing field mode, and thedisplay content of the display portion is made unviewable beyond acertain viewing angle by the use of the cancelling data displayed on theviewing angle controller. The fifth embodiment of the present invention,however, differs from these embodiments in that the viewing angles areswitched by changing the viewing angle characteristics of the viewingangle controller and the display portion so that the viewing anglecontroller and the display portion perform normal display in a wideviewing field mode, whereas the viewing angle controller performs darkdisplay in a narrow viewing field mode, and normal display is performedin the display portion having narrow viewing field characteristics. FIG.16 is a cross-sectional view of an internal semi-transmissive liquidcrystal display device according to the fifth embodiment. Table 4 is adiagram showing the operation of the reflective portion and thetransmissive portion in a wide viewing field mode and a narrow viewingfield mode in the fifth embodiment.

TABLE 4 Wide viewing field mode Narrow viewing field mode ReflectiveTransmissive Reflective Transmissive portion portion portion portionNormal Normal display Dark Normal display display

The arrangement of the fifth embodiment shall be described withreference to FIG. 16. As shown in FIG. 16A, the semi-transmissive liquidcrystal display device according to the present embodiment comprises abacklight 6 and an internal semi-transmissive liquid crystal panel 4positioned over the backlight 6. A reflective portion provided with aninternally reflective plate 5, and a transmissive portion fortransmitting light that is output from the backlight are disposed ineach pixel of the internal semi-transmissive liquid crystal displaydevice, making it possible for different voltages to be applied to thereflective portion and the transmissive portion. Additionally, thereflective portion has the viewing angle characteristics of a wideviewing field that allow a wide viewing field mode to be maintained inan individual manner, while the transmissive portion has the viewingangle characteristics of a narrow viewing field that allow a narrowviewing field mode to be maintained in an independent manner.

As shown in Table 4, normal display is performed by the reflectiveportion and the transmissive portion in a wide viewing field mode. Asshown in FIG. 16A, reflected display light 8 reflected by the internallyreflective plate 5 in the reflective portion has the viewing anglecharacteristics of a wide viewing field, while transmitted display light7 that is output from the backlight 6 and transmitted through the liquidcrystal panel has the viewing angle characteristics of a narrow viewingfield. The reflected display light 8 and transmitted display light 7 arecombined, producing the viewing angle characteristics of the wideviewing field. As shown in Table 4, in a narrow viewing field mode, thereflective portion performs dark display, while normal display isperformed in the transmissive portion. In this case, as shown in FIG.16B, since display is carried out solely with the viewing anglecharacteristics of a narrow viewing field display in the transmissiveportion, the viewing angle characteristics of the narrow viewing fieldare attained. Consequently, it is possible to switch the viewing anglebetween the wide viewing field mode and the narrow viewing field mode byswitching the display of the reflective portion. It is sufficient forthe viewing angle characteristics of the reflective portion to becharacteristics that afford a wide viewing field when combined with thenarrow viewing field of the transmissive portion. In the presentembodiment, the transmissive portion that performs normal display in thewide viewing field mode and the narrow viewing field mode can bealternatively understood as being the display portion, and thereflective portion used for switching the viewing angle as the viewingangle controller. The viewing angle characteristics of the reflectiveportion may be arbitrary characteristics derived by designing thereflective plate in a particular way. The viewing angle characteristicsof a narrow viewing field in the transmissive portion may be derivedthrough the use of a highly directional backlight, a louver, or thelike.

Next, a sixth embodiment of the present invention shall be described. Inthe fifth embodiment, the reflective portion has the viewing anglecharacteristics of a wide viewing field while the transmissive portionhas the viewing angle characteristics of a narrow viewing field, whereasthe sixth embodiment differs therefrom in that the reflective portionhas the viewing angle characteristics of a narrow viewing field whilethe transmissive portion has the viewing angle characteristics of a wideviewing field. FIG. 17 is a cross-sectional view of an internalsemi-transmissive liquid crystal display device according to the sixthembodiment. Table 5 is a diagram showing the operation of the reflectiveportion and the transmissive portion in a wide viewing field mode and anarrow viewing field mode in the sixth embodiment.

TABLE 5 Wide viewing field mode Narrow viewing field mode ReflectiveTransmissive Reflective Transmissive portion portion portion portionNormal Normal Normal Dark display display display

In the semi-transmissive liquid crystal display device according to thepresent embodiment, each single pixel is provided with a reflectiveportion and a transmissive portion, making it possible to applydifferent voltages to the reflective portion and the transmissiveportion. Additionally, the reflective portion has the viewing anglecharacteristics of a narrow viewing field display, while thetransmissive portion has the viewing angle characteristics of a wideviewing field. As shown in Table 5, normal display is performed in thereflective portion and the transmissive portion in a wide viewing fieldmode. As shown in FIG. 17A, reflected display light 10 reflected by theinternally reflective plate 5 in the reflective portion has the viewingangle characteristics of a narrow viewing field display, whiletransmitted display light 9 that is output from the backlight 6 andtransmitted through the liquid crystal panel has the viewing anglecharacteristics of a wide viewing field display. The reflected displaylight 10 and transmitted display light 9 are combined, producing theviewing angle characteristics of the wide viewing field. As shown inTable 5, in a narrow viewing field mode, the reflective portion performsnormal display, while the transmissive portion performs dark display. Asshown in FIG. 17B, since display is carried out with the viewing anglecharacteristics of a narrow viewing field in the reflective portiononly, the viewing angle characteristics of the narrow viewing field areattained. Consequently, it is possible to switch the viewing anglebetween the wide viewing field mode and the narrow viewing field mode byswitching the display of the transmissive portion. In the presentembodiment, the reflective portion that performs normal display in thewide viewing field mode and the narrow viewing field mode can bealternatively understood as being the display portion, and thetransmissive portion used for switching the viewing angle as the viewingangle controller.

Next, a seventh embodiment of the present invention shall be described.In the present embodiment, a transmitting/scattering switch element anda louver are disposed between the backlight and the polarizing platedisposed towards the backlight. FIG. 18 is a cross-sectional view of aninternal semi-transmissive liquid crystal display device according tothe seventh embodiment.

As shown in FIG. 18, in the present embodiment, a backlight 6 isprovided, and above the backlight 6 is disposed a louver 30 forregulated output of the direction of light incident from the backlight6. The louver 30 is composed of transparent regions 30 a that transmitlight, and absorbent regions 30 b that absorb light, arranged inalternating fashion in a direction parallel to the louver 30 surface. Atransmitting/scattering switch element 31 switchable between a lighttransmitting state and a scattering state is disposed above the louver30. In the transmitting/scattering switch element 31, polymer-dispersedliquid crystals 29 composed of liquid crystal regions 29 b dispersedthrough a polymer film 29 a are sandwiched between two electrodes 28disposed covering the surfaces of substrates 27. A liquid crystal panelis disposed above the transmitting/scattering switch element 31 and isdesigned in the same way as the liquid crystal panel in the firstembodiment, for example. The assigned symbols are the same as for theliquid crystal panel shown in FIG. 7, and no further description isgiven. In the present embodiment, by providing thetransmitting/scattering switch element 31 and the louver 30, the viewingangle can be switched irrespective of the display of the reflectiveportion 17. Specifically, whereas in the first through fourthembodiments, cancelling data display by the reflective portion sometimesfails to provide sufficient luminance in cases in which outside light isabsent or the outside light is weak so that the function of switchingthe viewing angle is sometimes lost, in the present embodiment, theviewing angle can be switched even under such circumstances.

Switching of the viewing angle is also possible by a method wherein, ina wide viewing field mode, the reflective portion 17 performs normaldisplay or dark display while the transmissive portion 18 performsnormal display in the wide viewing field (switched by thetransmitting/scattering switch element 31), whereas in a narrow viewingfield mode, the reflective portion 17 performs dark display while thetransmissive portion 18 performs normal display in the narrow viewingfield (switched by the transmitting/scattering switch element 31).

Next, an eighth embodiment of the present invention shall be described.In the eighth embodiment, a front light is provided on the side facingthe observer. FIG. 19 is a cross-sectional view of an internalsemi-transmissive liquid crystal display device according to the eighthembodiment. As shown in FIG. 19, a backlight 6 is provided in thepresent embodiment, and above the backlight 6 is positioned the liquidcrystal panel in the first embodiment, for example. A front light 32 isdisposed above the liquid crystal panel, and light is directed to beincident on the liquid crystal panel. In the first through sixthembodiments, normal display/dark display by the reflective portionsometimes fails to provide sufficient luminance in cases in whichoutside light is absent or the outside light is weak so that thefunction of switching the viewing angle is sometimes lost. However,providing the front light 32 allows the front light 32 to affordsufficient luminance under such circumstances, making it possible toswitch the viewing angle.

When the viewing angle controller displays pseudo-color by thereflective portion, it is acceptable for the front light 32 to producepseudo-colored light similar to the pseudo-color displayed by theviewing angle controller, instead of white light. By having the frontlight 32 produce pseudo-colored light similar to the pseudo-colordisplayed by the viewing angle controller, light absorbed by the colorfilter of the reflective portion that constitutes the viewing anglecontroller is reduced, and the utilization efficiency of the light ofthe front light 32 increases. Thus, as long as the luminance is the sameas that of the pseudo-colored display of the viewing angle controller,it is possible to lower power consumption by the front light 32.

Next, a ninth embodiment of the present invention shall be described.The ninth embodiment is an external semi-transmissive type, rather thanthe internal semi-transmissive type up to this point. FIG. 20 is across-sectional view of an external semi-transmissive liquid crystaldisplay device provided with a polarized light reflecting plateaccording to the ninth embodiment. FIG. 21 is a cross-sectional view ofan external semi-transmissive liquid crystal display device providedwith a semi-transmissive reflecting plate according to a modifiedexample of the ninth embodiment. Table 6 is a first illustration thatshows operation of the viewing angle controller and the display portionin a wide viewing field mode and a narrow viewing field mode in theninth embodiment. Table 7 is a second illustration that shows operationof the viewing angle controller and the display portion in a wideviewing field mode and a narrow viewing field mode in the firstembodiment.

First, the arrangement of the ninth embodiment shall be described usingFIG. 20. As shown in FIG. 20, a backlight 6 is provided in the presentembodiment, and above the backlight 6 is positioned a liquid crystalelement having a liquid crystal layer 16 sandwiched by two opposingsubstrates 12. A phase difference plate 35 is disposed on the upper faceof the substrate 12 disposed towards the observer, and a polarizingplate 11 is disposed thereon. A reflective polarizing plate 36 forselectively reflecting a prescribed deflection component of incidentlight incident from the display screen side is placed on the upper faceof the substrate 12 disposed towards the backlight 6; a phase differenceplate 35 is provided so as to cover the reflective polarizing plate 36;and additionally a polarizing plate 11 is provided so as to cover thephase difference plate 35. A viewing angle controller pixel electrode 33and a display portion pixel electrode 34 are separately formed on thesubstrate 12 disposed toward the backlight 6. The electrodes are formedon the side of the substrate that faces the observer. A shared COMelectrode 13 is formed on the opposite side of the substrate 12 disposedopposite the first substrate.

Next, the arrangement of the modified example of the ninth embodimentshall be described using FIG. 21. Two opposing substrates 12 arepositioned above a backlight 6, and a liquid crystal layer 16 issandwiched between the substrates. Polarizing plates 11 are disposed oneach of the two substrates 12. The plates are disposed on the sides thatare opposite from the sides that face each other. The polarizing plate11 disposed facing the backlight 6 is provided with a semi-transmissivereflective plate 39. The reflective plate is disposed on the side of thepolarizing plate that faces the backlight 6. The liquid crystal displayelement constitutes a transmissive/reflective portion. The substrate 12disposed facing the backlight 6 is provided with a viewing anglecontroller pixel electrode 33 and a display portion pixel electrode 34.The electrodes are formed separately on the side that faces theobserver. A shared COM electrode 13 is formed on the opposite side ofthe substrate 12 positioned opposite the first substrate. FIG. 21, whichshows the modified example of the ninth embodiment, is substantiallyidentical in arrangement to the ninth embodiment, apart from the factthat the semi-transmissive reflective plate 39 is used instead of thereflective polarizing plate 36 in FIG. 20.

In the external semi-transmissive type, there is no difference betweenthe reflective portion and the transmissive portion, and the reflectiveportion and the transmissive portion are integral. However, to switchthe viewing angle, each single pixel is provided with a viewing anglecontroller 37 used primarily for reflective display, and a displayportion 38 used primarily for transmissive display. To make it possiblefor different voltages to be applied to the viewing angle controller 37and the display portion 38, either the pixel electrodes are divided andprovided with respective TFTs, as in the first or third embodiments, orthe COM electrodes are divided and controlled independently, as in thesecond or fourth embodiments.

Next, the operation and effects of the ninth embodiment and the modifiedexample thereof shall be discussed using Table 6. As shown in Table 6,both the display portion and the viewing angle controller perform normaldisplay well in a wide viewing field mode. On the other hand, in anarrow viewing field mode, the display portion performs normal display,but the viewing angle controller assumes the bright state. A design istherefore adopted so that the luminance of the viewing angle controlleris greater than the luminance of the display portion beyond a specificviewing angle, in the same way as FIG. 9, which shows the viewingangle-luminance characteristics of the first embodiment, making itpossible for the display content of the display portion to be viewedfrom beyond the specific viewing angle. Consequently, it is possible toswitch the viewing angle between the wide viewing field mode and narrowviewing field mode by switching the display of the viewing anglecontroller. As shown in Table 7, in a wide viewing field mode, thedisplay portion may perform normal display while the viewing anglecontroller performs dark display (black display).

TABLE 6 Wide viewing field mode Narrow viewing field mode ViewingViewing angle Display angle Display controller portion controllerportion Transmission Normal Normal Transmission Bright Normal displaydisplay display Reflection Normal Normal Reflection Bright Normaldisplay display display

In a narrow viewing field mode, the viewing angle controller is notlimited to the bright condition (white display) of the three pixels RGB,and intermediate luminance or pseudo-color display is also acceptable aslong as the display content of the display portion is unviewable fromwithin the range 3 of restricted viewing angles. In a wide viewing fieldmode, display may be performed with the viewing angle controller and thedisplay portion of one pixel functioning as two pixels.

Next, a tenth embodiment of the present invention shall be described. Inthe first through fourth and the ninth embodiments, the viewing anglecontrollers of all of the pixels of the liquid crystal panel displaycancelling data in a narrow viewing field mode. In the tenth embodimentof the present invention, however, even in a narrow viewing field modethe viewing angle controllers of some of the pixels of the liquidcrystal panel perform normal display or black display.

TABLE 7 Wide viewing field mode Narrow viewing field mode ViewingViewing angle display angle Display controller portion controllerportion Transmission DARK Normal Transmission Bright Normal displaydisplay Reflection dark Normal Reflection Bright Normal display display

FIG. 22 is a diagram showing the operation in the viewing anglecontroller and the pixel units of the display portion in a wide viewingfield mode and a narrow viewing field mode of the first to fourth andninth embodiments. FIG. 23 is a diagram showing the operation in theviewing angle controller and the pixel units of the display portion in anarrow viewing field mode in the tenth embodiment.

As shown in FIG. 22A, in the first to fourth and the ninth embodiments,the viewing angle controller 37 of the pixel 45 performs normal displayor black display, and the display portion 38 performs normal display ina wide viewing field mode for all of the pixels of the liquid crystalpanel. As shown in FIG. 22B, the viewing angle controller 37 of thepixel 45 performs cancelling data display, and the display portion 38performs normal display in a narrow viewing field mode for all of thepixels of the liquid crystal panel.

In the tenth embodiment of the present invention, operation duringviewing in a wide field is the same as that shown in FIG. 22A. In anarrow viewing field mode, however, some of the viewing anglecontrollers 37 perform normal display or black display in the mannershown in FIG. 23A, rather than the viewing angle controllers 37 of allof the pixels of the liquid crystal panel performing cancelling datadisplay. At this time, there is a visible difference between the normaldisplay and cancelling data display, or the black display and cancellingdata display of the viewing angle controllers, when viewed from a wideangle range having a restricted viewing angle. Consequently, the normaldisplay or black display is arranged as a design, a picture, or othersuch image pattern in the viewing angle controllers in the narrowviewing field mode, making it possible to produce an image patternviewable from a wide angle range having a restricted viewing angle.

With the method described above, initially the image pattern will beobserved in a narrow viewing field mode when a fixed image patternviewable from a wide angle range having a restricted viewing angle isdisplayed, but as the eye becomes accustomed it will become possible toview the display content of the display portions of pixels whose viewingangle controllers are performing normal display or black display. Inorder to prevent this, at certain time intervals the image pattern movesor flashes, or a different image pattern is displayed (FIG. 23B). Thatis, in preferred practice, the image pattern produced at the throughplacement of normal display or black display by the viewing anglecontrollers in a narrow viewing field mode will vary spatially,temporally, or spatiotemporally.

Next, an eleventh embodiment of the present invention shall bedescribed. In the fifth and sixth embodiments, the viewing anglecontroller performs dark display in a narrow viewing field mode in allof the pixels of the liquid crystal panel. In the eleventh embodiment ofthe present invention, however, normal display is performed by theviewing angle controller in some of the pixels of the liquid crystalpanel even in a narrow viewing field mode.

FIG. 24 is a diagram showing the operation in the viewing anglecontroller and the pixel units of the display portion in a wide viewingfield mode and a narrow viewing field mode of the fifth and sixthembodiments. FIG. 25 is a diagram showing the operation in the viewingangle controller and the pixel units of the display portion in a narrowviewing field mode in the eleventh embodiment.

As shown in FIG. 24A, in the fifth and sixth embodiments, the viewingangle controller 37 of the pixel 45 performs normal display, and thedisplay portion 38 performs normal display in all of the pixels of theliquid crystal panel in a wide viewing field mode. As shown in FIG. 24B,the viewing angle controller 37 of the pixel 45 performs black display,and the display portion 38 performs normal display in all of the pixelsof the liquid crystal panel in a narrow viewing field mode.

In the eleventh embodiment of the present invention, on the other hand,operation during viewing in a wide field is the same as that shown inFIG. 24A. In a narrow viewing field mode, however, some of the viewingangle controllers perform normal display (FIG. 25A) rather than theviewing angle controllers of all of the pixels of the liquid crystalpanel performing normal display. At this time, there is a visibledifference between normal display and black display by the viewing anglecontrollers 37 when viewed from a wide angle range having a restrictedviewing angle. Consequently, the normal display is arranged as a design,a picture, or other such image pattern in the viewing angle controllers37 in the narrow viewing field mode, making it possible to produce animage pattern viewable from a wide angle range. As in the tenthembodiment, at certain time intervals the image pattern may move orflash, or a different image pattern may be displayed (FIG. 25B).

FIG. 26 is a perspective view showing a portable terminal deviceequipped with the liquid crystal display device according to a twelfthembodiment of the present invention. As shown in FIG. 26, the liquidcrystal display portion 44 of the present invention may be installed ina mobile phone 43, for example. The liquid crystal display device of thepresent invention can be implemented favorably in a mobile phone orother such portable device, making it possible to switch the viewingangle display in the display device installed in the portable device.The portable device is not limited to a mobile phone, and the inventioncan be implemented advantageously in portable devices of various kinds,such as PDAs, game devices, digital cameras, digital video cameras, andthe like.

1-26. (canceled)
 27. A semi-transmissive liquid crystal display devicecomprising: a liquid crystal panel provided with a liquid crystal layerbetween two substrates having electrodes formed thereon; a backlight foroutputting light to the liquid crystal panel; and a controller forcontrolling a voltage applied to the liquid crystal layer; wherein eachof pixels of the liquid crystal panel individually has a reflectiveportion for reflecting and displaying light incident from the displayscreen side, and a transmissive portion for transmitting and displayinglight that is output by said backlight; the reflective portion has wideviewing angle characteristics, and the transmissive portion has narrowviewing angle characteristics, and the controller controls,independently for said reflective portion and the transmissive portion,the voltage applied to the liquid crystal layer, and switches a viewingangle between a wide viewing field mode and a narrow viewing field modeby performing control so that, in the wide viewing field mode, thereflective portion performs normal display while the transmissiveportion performs normal display, whereas in the narrow viewing fieldmode the reflective portion performs dark display while the transmissiveportion performs normal display.
 28. A semi-transmissive liquid crystaldisplay device comprising: a liquid crystal panel provided with a liquidcrystal layer between two substrates having electrodes formed thereon; abacklight for outputting light to the liquid crystal panel; and acontroller for controlling a voltage applied to the liquid crystallayer; wherein each of pixels of the liquid crystal panel individuallyhas a reflective portion for reflecting and displaying light incidentfrom the display screen side, and a transmissive portion fortransmitting and displaying light that is output by the backlight; thereflective portion has narrow viewing angle characteristics and thetransmissive portion has wide viewing angle characteristics, and thecontroller controls, independently for the reflective portion and thetransmissive portion, the voltage applied to the liquid crystal layer,and switches a viewing angle between a wide viewing field mode and anarrow viewing field mode by performing control so that in the wideviewing field mode the reflective portion performs normal display whilesaid transmissive portion performs normal display, whereas in the narrowviewing field mode the reflective portion performs normal display whilesaid transmissive portion performs dark display.
 29. Thesemi-transmissive liquid crystal display device according to claim 27,wherein the reflective portions of part of the pixels perform normaldisplay instead of dark display in the narrow viewing field mode, sothat an image pattern is displayed.
 30. The semi-transmissive liquidcrystal display device according to claim 28, wherein the transmissiveportions of part of the pixels perfotin normal display instead of darkdisplay in the narrow viewing field mode, so that an image pattern isdisplayed.
 31. The semi-transmissive liquid crystal display deviceaccording to claim 29, wherein the display of the image pattern in thenarrow viewing field mode varies spatially, temporally, orspatiotemporally.
 32. The semi-transmissive liquid crystal displaydevice according to claim 30, wherein the display of the image patternin the narrow viewing field mode varies spatially, temporally, orspatiotemporally.
 33. A portable terminal device comprising thesemi-transmissive liquid crystal display device according to claim 27.34. A portable terminal device comprising the semi-transmissive liquidcrystal display device according to claim 28.